What are Pneumatic Cylinders?

Pneumatic cylinders are mechanical devices that generate force through pressurized air. They typically include a piston, piston rod, and a cylinder. As air enters one side of the cylinder, the internal pressure increases, causing the piston to move in a specific direction. The piston rod then transfers the resulting force to the object being moved.

The working fluid in pneumatic cylinders is compressed air. Hence, pneumatic cylinders are desirable for environments requiring a high level of cleanliness, as the fluid will not contaminate the surroundings in case of leakage. Pneumatic cylinders operate quietly and do not require large storage tanks for the working fluid.

Pneumatic cylinders play a crucial role in automating machinery and industrial processes. They provide force and motion for various functions, including clamping, ejecting, blocking, and lifting. In manufacturing environments, they are often employed for repetitive tasks such as transferring objects to and from machines or equipment. Additionally, pneumatic cylinders are utilized in piping systems to control valve operations.

What are the components of pneumatic cylinders?

Here are the main components of pneumatic cylinders:

Pneumatic Cylinder Bore: The pneumatic cylinder bore houses and protects the internal components. It is closed by two end caps: the front-end (cylinder head) and the rear-end (cylinder cap). The front-end cap is located adjacent to where the piston rod extends while the rear-end cap is mounted on the opposite side. One or both caps have ports that introduce pressurized air inside the bore. Seals with cushioning capability are placed between the bore and the caps to prevent leakage and high impact during actuation.

• Piston: The piston is the disc inside the pneumatic cylinder, which serves as a movable partition that divides the chamber. It reciprocates back and forth in a straight line. As compressed air enters the port of the rear-end cap, it exerts pressure on the piston, which causes it to move away from the rear-end cap and for the piston rod to protrude. This movement is called positive or plus movement and the pressurized chamber which causes this movement is called the plus chamber. The minus chamber is located on the opposite side. The piston then returns to its original position. The manner of how the piston returns to its original position depends on its type. The amount of force generated by the pneumatic cylinder is equivalent to the air pressure multiplied by the area of the piston. The diameter of the pneumatic cylinder refers to the diameter of the piston or the inner diameter of the cylinder.

• Piston Rod: The piston rod is connected and driven by the piston. It is attached to the machine element or objects to be pushed or pulled. The stroke length refers to the distance that the piston and the piston rod have traveled.

• Piston Cushioning: The piston cushioning lowers the speed of the piston and rod assembly before it reaches the end cap. It helps to reduce impact, noise, and vibration at the end of every stroke and enables the piston to move at faster velocities.

• Piston Static Seal: The piston static seal ensures an airtight sealing between the piston and the rod.

• Piston Seal: A piston seal ensures an airtight sealing between the piston and the chamber. It prevents air from leaking to the other side of the chamber.

• Piston Guide Rings: Piston guide rings prevent direct metallic contact between the piston and the cylindrical chamber during sliding motion. They absorb radial forces acting in the cylinder. They are mounted in the piston and made of chemical resistant, low friction, and self-lubricating plastics such as PTFE and polyamide.

• Sensors: Sensors are used to detect the linear position of the piston inside the cylinder. They are important for positioning applications. Reed switches and Hall-effect sensors are the commonly used pneumatic cylinder sensors.

• Tie Rods: Tie rods are the threaded steel rods that hold the end caps to the pneumatic cylinder bore. A static seal is present between the end cap and bore interface. The tie rods run around the length of the cylinder. A pneumatic cylinder can have 4-20 tie rods depending on the size and force it produces, which makes the cylinder bulkier. The tie rods also protect the cylinder from possible impact and shock.